This invention generally relates to an electrical terminal assembly and, more particularly, to a terminal assembly having mated male and female members which are easier, in terms of the required amount of force, to engage than to disengage.
Terminal assemblies are used in a wide variety of products having electrical components. These products range from simple electrical items, such as a lamp, to those with highly sophisticated electrical systems, such as an automobile.
One variety of terminal assembly uses a male member and a female member which are mated together along a mating axis. Typically, the members or the terminals, are formed by bending a stamped piece of conductive material into the desired configuration. When formed by bending, common terminal materials include nickel plated tin, stainless steel and beryllium copper. As an alternative, the female terminal can be formed by machining cast pieces of conductive material. When formed by casting and machining, one common terminal material is aluminum.
While mated terminals generally work well for their intended purposes, a number of problems can arise when the terminals are repeatedly engaged and disengaged from each other. One problem is that the terminals may become deformed. Deformation is particularly a problem when the male terminal is withdrawn from the female terminal at an angle with respect to the mating axis. Repeated insertion and withdrawal can also result in a decreased contact normal force, a loss in electrical interface integrity, material fatigue, and a decrease in the amount of force required for disengagement of the terminals. This latter problem allows the terminal assembly to be more susceptible to inadvertent disengagement.
To maintain a high resistance to withdrawal or disengagement, one solution is to create a "tighter fit" between the terminals and another is to use less resilient materials in forming the terminals. However, these solutions result in an increase in the force needed to insert the male terminal into the female terminal. Unfortunately, the requirement of a high insertion force is undesirable from a product assembly standpoint.
With the above limitations in mind, it is object of the present invention to provide a terminal assembly which requires a different amount of force for engagement than for disengagement. In particular, it is an object of this invention to provide a terminal assembly that can be easily engaged, but which is significantly harder to disengage.
Still another object of this invention is to provide a terminal assembly that maintains a high contact normal force between the terminals even after repeated engagement and disengagement of the terminals. A related object is therefore sustaining the electrical interface integrity between the terminals after repeated engagement and disengagement.
A further object of this invention is to provide a terminal assembly which resists deformation of the individual terminals as a result of them being pulled apart or disengaged at an angle relative to each other or off line of the mating axis.
In achieving these an other objects, the present invention provides a terminal assembly which has male and female members that are adapted for mated engagement along a mating axis. The lead end of the male member is inserted into the female member of the assembly and a first ramping surface, which is inclined proceeding away from the lead end, is defined on the male member at a predetermined ramp angle with respect to the mating axis. A second ramping surface, adjacent to the first, is formed on the male member so as to define another ramp angle with respect to the mating axis. The second ramping surface, however, is declined in a direction proceeding away from the lead end. The male member is longitudinally divided in half so that the first and second ramping surfaces are both formed on a pair of resilient arms. The arms operate as a means for biasing the first and second ramping surfaces outward, from the mating axis, and allow the male member to be repeatedly inserted and withdrawn without deformation of its overall shape. To require different insertion and withdrawal forces, the ramp angle defined by the first ramping surface is less than the ramp angle defined by the second ramping surface.
When the male and female members are being engaged with each other, the first ramping surface contacts a correspondingly angled surface on the female member. The inherent biasing of the resilient arms cooperate with the shallow first ramp angle to provide a minimum amount of resistance to engagement. However, during withdrawal of the male member from female member, the biasing of the arms cooperates with the steeper ramp angle of the second ramping surface, and a correspondingly angled surface on the female member, to provide a significantly greater amount of resistance.
By constructing the male terminal with a pair of resilient arms, it is possible for the terminals of the assembly to be angularly disengaged from each other without resulting in the terminals becoming deformed as a result of the off-line withdrawal. Similarly, the bias of the arms ensures that a high contact normal force is maintained thereby sustaining the electrical interface integrity of the mated assembly.
Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which this invention relates from the subsequent description of the preferred embodiments and the appended claims taken in conjunction with the accompanying drawings.